The present invention relates in general to hydrodynamic drives, and more particularly, to a twin-flow modulated torque converter.
Prior art torque converters incorporate at least one of three basic elements: a rotatable bladed pump or impeller member which is coupled to the input or drive shaft of a prime mover; a rotatable bladed turbine or runner member coupled to an output or driven shaft; and a reactor or stator member positioned between the outlet of the turbine member and the inlet of the pump for directing the flow of the fluid discharged by the turbine before redirecting same to the pump. In addition to these three basic elements, some prior art structures have employed means to interrupt and/or to modulate the hydrodynamic power transmission from the prime mover to output drive means for varying the torque absorbed or the power transmitted at any predetermined input speed.
Some prior art devices employed mechanical clutch elements between the input shaft and the torque converter, such as the Omega Drive System of Twin Disc Inc., for modulating the torque between the input and the output drives. The slippage of the clutch surfaces is controlled to proportion the input power between the torque converter input and the torque converter output shaft. Although full modulation can be achieved, these devices are undesirable because the overall efficiency of the system is reduced through dissipation of energy through the heat buildup between the clutch surfaces. Moreover, the attendant wear of the clutch surfaces requires frequent adjustment and replacement.
Other prior art devices, such as the Buick Variable-Pitch Dynaflow Torque Converter, employed devices to alter the pitch of the reactor blades to modulate the torque absorption characteristics of the torque converter. The range of modulation could be improved as it tended to be from 100% torque down to about 60% torque in operation. Moreover, each vane required a separate pivot mounting thereby increasing the complexity of the device as well as the likelihood of failure in operation.
Still other prior art devices utilize means for interrupting the fluid toric flow in operation. Exemplary of these devices are the patents to Audiffred et al, U.S. Pat. No. 3,673,799 and R. T. Burnett, U.S. Pat. No. 2,580,072. Both structures are designed to temporarily reduce the torque output when a multispeed transmission is shifted into a different gear. Since both devices function to block the hydrodynamic flow in the torque converter, the total energy input thereto must be largely dissipated in heat. Accordingly, both devices may be engaged only briefly in order to avoid excessive temperatures in the torque converter. Also the full input power of these devices cannot be made available for other purposes when the fluid path in the torus is blocked.
The present invention circumvents the above disadvantages of the prior art by providing a torque converter with twin flow circuits in the torus to approach full-range modulation with little energy dissipated through heat. In one flow circuit, fluid flow passes normally through the pump, turbine, and reactor members to accomplish full power capacity. In one embodiment of the twin or alternate flow circuit, fluid flow to the turbine member is interrupted and directed through a fluid bypass formed in the rings of the pump and turbine members, to effect minimum drive through the torque converter while continuing the pump rotation for driving a power take-off shaft. The bypass circuit is normally closed by the ring of the reactor member, which is adapted for linear movement in varying positions so that intermediate stages of modulation between the minimum and the maximum can be achieved as well.
In another embodiment of the present invention, the pump and turbine members are adapted to move relative to each other for varying the cross section area of the fluid bypass. Through this feature, the overall performance of the torque converter will be enhanced.
Accordingly, the instant invention effects substantially complete and continuous interruption of the toric flow, which drives the turbine member, by diverting same through the bypass circuit without experiencing overheating or loss of input power as in the prior art structures. Accordingly, substantially full-range modulation can be achieved over an extended time.
Moreover, the torque converter of the present invention requires no clutch mechanisms to modulate power thereby experiencing longer life through less wear and greater efficiency through less energy dissipation through heat. Also, the torque converter of the present invention eliminates complex mechanical features, such as variable pitch reactor vanes, thereby being more reliable in operation while permitting wider range of vehicle drive torques and speeds.